Riikka Kalliokoski | PubMed Health

PubMed2004

Assessment of right ventricular oxidative metabolism by PET in patients with idiopathic dilated cardiomyopathy undergoing cardiac resynchronization therapy.

PURPOSE: Right ventricular (RV) performance is known to have prognostic value in patients with congestive heart failure (CHF). Cardiac resynchronization therapy (CRT) has been found to enhance left ventricular (LV) energetics and metabolic reserve in patients with heart failure. The interplay between the LV and RV may play an important role in CRT response. The purpose of the study was to investigate RV oxidative metabolism, metabolic reserve and the effects of CRT in patients with CHF and left bundle brach block. In addition, the role of the RV in the response to CRT was evaluated. METHODS: Ten patients with idiopathic dilated cardiomyopathy who had undergone implantation of a biventricular pacemaker 8+/-5 months earlier were studied under two conditions: CRT ON and after CRT had been switched OFF for 24 h. Oxidative metabolism was measured using [11C]acetate positron emission tomography (Kmono). The measurements were performed at rest and during dobutamine-induced stress (5 microg/kg per minute). LV performance and interventricular mechanical delay (interventricular asynchrony) were measured using echocardiography. RESULTS: CRT had no effect on RV Kmono at rest (ON: 0.052+/-0.014, OFF: 0.047+/-0.018, NS). Dobutamine-induced stress increased RV Kmono significantly under both conditions but oxidative metabolism was more enhanced when CRT was ON (0.076+/-0.026 vs 0.065+/-0.027, p=0.003). CRT shortened interventricular delay significantly (45+/-33 vs 19+/-35 ms, p=0.05). In five patients the response to CRT was striking (32% increase in mean LV stroke volume, range 18-36%), while in the other five patients no response was observed (mean change +2%, range -6% to +4%). RV Kmono and LV stroke volume response to CRT correlated inversely (r=-0.66, p=0.034). None of the other measured parameters, including all LV parameters and electromechanical parameters, were associated with the response to CRT. In responders, RV Kmono with CRT OFF was significantly lower than in non-responders (0.036+/-0.01 vs 0.058+/-0.02, p=0.047). CONCLUSION: CRT appears to enhance RV oxidative metabolism and metabolic reserve during stress. Patients responding to CRT appear to have lower RV oxidative metabolism at rest, suggesting that the RV plays a significant role in the response to CRT.

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PubMed2004

The effects of cardiac resynchronization therapy on left ventricular function, myocardial energetics, and metabolic reserve in patients with dilated cardiomyopathy and heart failure.

OBJECTIVES: The effects of long-term cardiac resynchronization therapy (CRT) on left ventricular (LV) energetics and metabolic reserve were evaluated. BACKGROUND: Cardiac resynchronization therapy is a new therapy for patients with drug-refractory severe heart failure (HF). METHODS: Ten patients with idiopathic dilated cardiomyopathy who had undergone implantation of biventricular pacemaker 8 +/- 5 months earlier were studied during two conditions: CRT switched on, and after CRT was switched off for 24 h. Left ventricular function was measured using echocardiography and oxidative metabolism using [(11)C]acetate positron emission tomography. Both measurements were performed at rest and during dobutamine-induced stress (5 microg/kg/min). Basal- and adenosine-stimulated (140 microg/kg/min) myocardial blood flow were quantitated using [(15)O]water. RESULTS: During CRT off, LV stroke volume was significantly reduced at rest (72 +/- 18 ml vs. 63 +/- 15 ml, p < 0.05), but LV oxidative metabolism (K(mono)) remained unchanged (0.046 +/- 0.008 vs. 0.054 +/- 0.016 min(-1)) leading to a significant deterioration of myocardial efficiency of forward work (from 48.2 +/- 16.7 to 36.6 +/- 11.7 mm Hg.l/g, p < 0.05). During dobutamine-induced stress, stroke volume and K(mono) values were not different whether CRT was on or off. However, myocardial efficiency (56.1 +/- 16.1 vs. 49.8 +/- 18.0 mm Hg.ml.g(-1).min(-1), p = 0.099) and metabolic reserve, the response of K(mono) to dobutamine (0.023 +/- 0.014 vs. 0.013 +/- 0.014 min(-1), p = 0.09), tended to reduce when CRT was switched off. Cardiac resynchronization therapy had no effects on myocardial perfusion. Natriuretic peptides increased significantly during CRT-off period. CONCLUSIONS: Long-term CRT has beneficial effects on LV function and myocardial efficiency at rest in patients with HF. These effects are not associated with changes in myocardial perfusion or oxygen consumption. During dobutamine-induced stress, CRT does not affect functional parameters, but myocardial efficiency and metabolic reserve may be increased.

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